Referring to FIGS. 1 and 2, a conventional method for making a carbon fiber wheel rim includes the steps of: forming a rim frame 10 that is configured to have a substantially U-shaped or triangular cross-section; and attaching an engaging seat 11, which is for engagement with a tire and is configured to have an H-shaped cross-section, onto an annular outer surface of the rim frame 10. The rim frame 10, as well as the engaging seat 11, is formed by interlacingly attaching a plurality of carbon-fiber fabrics 12, which are cut into strips, onto an assembly of an airbag 14 (e.g., as described in Taiwanese Patent No. I434771) and a reinforcement piece 13, followed by heating and pressing the carbon-fiber fabrics 12 to obtain the carbon fiber wheel rim.
However, while attaching the carbon-fiber fabric 12 to form the rim frame 10 and the engaging seat 11, 6 to 8 pieces of the carbon-fiber fabrics 12 are required to be attached onto the assembly for constituting each side surface of the rim frame 10 and the engaging seat 11. In addition, such attachment can only be performed manually, in other words, the process of forming either one of the rim frame 10 and the engaging seat 11 requires attaching the carbon-fiber fabrics 12 for at least 36 times. Such process is time consuming and results in relatively low production efficiency and relatively high production cost. Moreover, carbon fibers in the carbon fiber fabrics 12 do not unidirectionally extend and are discontinued at edges of the carbon-fiber fabrics 12, resulting in decreased mechanical strength at the edges. Furthermore, the interlacing arrangement of the carbon-fiber fabrics 12 may result in an uneven surface profile (e.g., gaps may occur at overlapping sites of the carbon-fiber fabrics 12) and cause formation of bubbles during the heating and pressing step so that production yield is decreased. Even further, the rim frame 10 and the engaging seat 11 are not integrally formed as one piece, thereby decreasing the overall structural strength of the carbon-fiber wheel rim.
Taiwanese Patent No. I382926 discloses another conventional method for making a carbon-fiber wheel rim, including steps of: winding continuously a carbon-fiber strip provided with an adhesive around a circular core; and placing the core with the carbon-fiber strip into a mold, followed by heating and pressing so as to obtain the carbon-fiber wheel rim. However, the carbon-fiber strip is relatively wide and may result in a relatively large amount of folds during the winding process, which may decrease the production yield of the carbon fiber wheel rim.